Median of Two Sorted Arrays

2013.12.1 19:29

There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).

 

Solution:

  Given two sorted array, find out the median of all elements. My solution is straightforward, merge two arrays and return the median.

  Time complexity is O(m + n), space complexity O(m + n) as well. In-place merge is too much trouble, and merging by swapping have some bad case of O(n^2) time compleity. So the direct solution is sometimes a wise solution at all :) 

  Here is the accepted code.

Accepted code:

 1 // 1RE 1AC
 2 class Solution {
 3 public:
 4     double findMedianSortedArrays(int A[], int m, int B[], int n) {
 5         // IMPORTANT: Please reset any member data you declared, as
 6         // the same Solution instance will be reused for each test case.
 7         merge(A, m, B, n);
 8         if((m + n) % 2 == 1){
 9             return C[(m + n - 1) / 2];
10         }else{
11             return (C[(m + n) / 2 - 1] + C[(m + n) / 2]) / 2.0;
12         }
13     }
14 private:
15     vector<int> C;
16     
17     void merge(int A[], int m, int B[], int n) {
18         C.clear();
19         
20         int i, j;
21         
22         i = j = 0; // Bugged here, omitted this sentence
23         while(i < m && j < n){
24             if(A[i] <= B[j]){
25                 C.push_back(A[i++]);
26             }else{
27                 C.push_back(B[j++]);
28             }
29         }
30         
31         while(i < m){
32             C.push_back(A[i++]);
33         }
34         
35         while(j < n){
36             C.push_back(B[j++]);
37         }
38     }
39 };

 

 posted on 2013-12-01 19:38  zhuli19901106  阅读(206)  评论(0编辑  收藏  举报